The present invention generally relates to a magnetic disc apparatus, and more particularly, to a head positioning assembly for a magnetic disc apparatus.
FIG. 1 is a plan view of one example of a conventional head positioning assembly for use in the magnetic disc apparatus and FIG. 2 is a perspective view of the head positioning assembly.
The conventional magnetic disc apparatus shown in FIGS. 1 and 2 comprises a disc drive assembly 1 disposed on a base (not shown) and a head positioning assembly 2 disposed on the base in a predetermined relationship with respect to the disc drive assembly 1. The disc drive assembly 1, which drives a magnetic disc 11 upon which magnetic recording and reproducing are achieved comprises a rotary shaft 12 by which the disc 11 is supported and a drive unit 13 for driving the shaft 12.
The head positioning assembly 2 for positioning a read and write head 21 comprises a suspension 22 which supports at one end thereof the head 21, a carriage 23, a pair of cylindrical guide rails 24a and 24b, a pair of flat guide rails 25a and 25b, an E shaped yoke 26 and a pair of magnets 27a and 27b (27b being invisible in the Figures.) mounted on inner side walls of both side legs of the E shaped yoke 26, the yoke 26 and magnets 27a and 27b together constituting a magnetic circuit which is fixedly mounted on the base (not shown) or the housing (not shown) of the magnetic disc apparatus.
The carriage 23 comprises an arm 32 extending from one end of the carriage 23 and has secured at the extnding end thereof the suspension 22, and a voice coil 34 mounted on the carriage 23. The voice coil 34 movably receives therein the center leg of the E shaped yoke 26. The carriage 23 further comprises two pairs of linear bearings 35a and 35b, and 35c and 35d provided on lower portions of the respective sides of the carriage 23, and one pair of linear bearings 36a and 36b provided on upper portions of the respective sides of the carriage 23. The carriage 23 is movably mounted on the pair of cylindrical guide rails 24a and 24b through the linear bearings 35a and 35b, and 35c and 35d. The carriage 23 is further supported by the pair of flat guide rails 25a and 25b through the linear bearings 36a and 36b, whereby, the guide rails 25a and 25b serve to stabilize the carriage 23 regardless of the level position of the magnetic disc apparatus.
When a current is applied to the voice coil 34, a magnetic field is generated around the windings thereof, the generated magnetic field of the magnets 27a and 27b generating a driving force to move the carriage 23 together with the head 21 in the direction of an arrow A or A' shown in FIG. 1. Since the disc 11 is disposed along one end of the carriage 23, the movement of the carriage 23 in the direction of travel A and A' causes the head 21 to move in the radial direction of the disc 11, thereby allowing for the accurate positioning of the head 21 at an objective track on the disc 11.
The thus constructed conventional magnetic disc apparatus has problems in that, when a larger driving force is required, it is necessary to increase the effective area of the winding of the voice coil 34. For this purpose, the length of the voice coil 34, i.e. length of the bobbin upon which the winding is wound, has to be elongated. However, since the disc is disposed at one end of the carriage 23, the head 21 is radially moved in the direction of travel A or A' of the carriage 23, which makes it difficult to increase the length of the bobbin within a specified dimension of an external storage housing (not shown), and in order to further increase the driving force, the depth of the external storage housing or the length thereof has to be elongated in the direction that the other end of the carriage 23 becomes distant from the rotary shaft 12 of the disc drive assembly 1.